Immersion means including work holder



Sept. 9, 1969 ca. L. HEIN 3,465,717

IMMERSION MEANS INCLUDING WORK HOLDER Filed March 4, 1965 5 Sheets-Sheet 1 INVENTOFZ GARY L. HEIN Sept. 9, 1969 5. L. HEIN IMMERSION MEANS INCLUDING WORK HOLDER 5 Sheets-Sheet 2 Filed March 4, 1965 DRY AT RAISED E AT PACKAGE DRY IN FREEZE AT LOW 40TO VACUUM H ABOUT -50C DRAIN EXCESS TEMP.

LIQUID LOAD I m I 18b II FIVV INVENTOQ L HEIN Sept. 9, 1969 G. L. HElN IMMERSION MEANS INCLUDING WORK HOLDER Filed March 4, 1965 3 Sheets-Sheet 5 INVENTOR GARY L. HEIN MW eflttys.

United States Patent 3,465,717 IMMERSION MEANS INCLUDING WORK HOLDER Gary L. Hein, Decatur, Ill., assignor to Lincoln Laboratories, Inc., Decatur, Ill., a corporation of Illinois Filed Mar. 4, 1965, Ser. No. 437,206 Int. Cl. 1505c 3/00, 11/14; B23q 1/00 U.S. Cl. 118-429 Claims ABSTRACT OF THE DISCLOSURE Apparatus, to dip multiple-point intradermal inoculators to effect uniform loading thereon, includes a plurality of elongated immersion tanks associated with means to circulate biological coating material and in combination with a work holder comprising bar means to slidingly receive the inoculators thereon and said bar means including rail elements to angularly retain said inoculators.

U.S. Patent No. 2,817,336. The said patent discloses, in

one form thereof, the combination of a multiple-point intradermal pressure-puncture instrument, or scarifier, and biological carried thereby to be applied to a selected skin area from the exterior of the multiple points of the instrument. A later U.S. Patent No. 3,136,314 discloses an improved multi-point instrument wherein the points thereof are clustered very closely together, so that a biological may be loaded onto the cluster of points to be retained thereon by surface tension prior to the instru ment being used to effect intradermal inoculation by scarification and simultaneous application of the biological to the scarified skin site.

It has been proposed to provide, as a further improved form of multiple-point biological applicator, for intradermal inoculation, an applicator of the type in Patent No. 3,136,314 which carries thereon a single-stable-dose of biological lyophilized in situ, so that the resultant combination provides a unitary device of increased shelf life, with the biological in dried form located in the space between pairs of adjacent points and precisely where it is to be used, so that upon reconstitution of the dried biological, it will be possible to effect application of the biological simultaneously with the effecting of the intradermal scarification. Such an improved device is disclosed in a co-pending application of Harvey Kravitz, Ser. No. 371,918, filed June 2, 1964 and now Patent No. 3,351,059.

It has been found however, that effective economical production of such an intradermal applicator which carries thereon a lyophilized single-stable-dose of biological is not a simple task. It was discovered to be impractical with existing techniques to merely attempt to press on, or cause the biological in dried form to be made to adhere to the points of a multiple-pressure instrument of ice Patent No. 3,136,314. Furthermore, it is extremely important in the mass production of such devices for administration of biologicals to be able to predict, or obtain, uniformity of dosage of the biological substance that is to be lyophilized on the scarifying instrument, and the said mechanical methods of loading, which would ordinarily suggest themselves for solution of the problem, appear, at present, to yield random size loadings and thus to be incapable of providing the requisite uniformity of dosage.

It has also been heretofore proposed in a multiple-point intradermal inoculator to provide a plurality of relatively widely spaced metal points or prongs wherein the surface of the prongs have had to be treated to provide thereon a plurality of very small openings, scratches, or roughening which afford retention on each individual prong of a greater amount of liquid biological that is later applied by dipping of the points, cataphoresis or electrophoresis. However, the random nature suggested of providing openings, scratches or roughening fails to provide a precisely uniform configuration which would insure effecting the loading of a precise dose of liquid biological, nor does it appear from such prior suggestion that a dip type loading would insure an accurate and automatic loading of a precise dosage of liquid on a multiple-point intradermal inoculator.

Thus, the object of this invention is to provide improved apparatus for production of an intradermal inoculator carrying a lyophilized single-stable-dose of biological thereon, whereby there is obtained substantial uniformity of dosage of the biological on the inoculator, in the preparation of the final product.

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection with the accompanying drawings, in which:

FIG. 1 is an illustrative fragmentary view of one type of apparatus for carrying out one method of loading of liquid onto the points of multiple-point pressure-puncture applicators, as part of the invention disclosed herein;

FIG. 2 is an enlarged fragmentary cross-section view taken on line 22 of FIG. 1 and showing the individual amount for each inoculator;

FIG. 3 is a fragmentary cross-section view of one form of the final packaged product;

FIG. 4 shows another form of the final packaged prod uct with a portion broken away to show details;

FIG. 5 is an illustrative flow chart showing major steps of the process embodying the invention herein;

FIG. 6 is an illustrative cross-section view of another device for carrying out the method of loading of liquid onto a plurality of multiple-point applicators;

FIG. 7 is a perspective view of the bath portion of the apparatus of FIG. 6;

FIG. 8 is a perspective view of the rack portion of the apparatus of FIG. 6, but shown in inverted position;

FIG. 9 is an enlarged fragmentary cross-section view taken on line 9-9 of FIG. 8; and

FIG. 10 illustrates a modified form of apparatus, using the rack structure of FIG. 8 but showing its adaptation for use with a drop-loading pipette system.

Referring now to the drawings, the figures illustrate generally different forms of apparatus for use in producing an intradermal inoculator of the type which carries thereon a single-stable-dose of biological. Basically, a supply of multiple-point, pressure-puncture-type inoculators with clustered points of the type disclosed in Patent No. 3,136,314, are provided and similarly disposed so that each is at an attitude such that, with a liquid disposed, or deposited, on the multiple points of the inoculator, gravity forces on the liquid normally tend to cause the liquid to run off the multiple points. Thus, the inoculators may be arranged in inclined attitude, as in FIG. 1, or in inverted attitudes as in FIG. 6. Then, a pre-selected amount of inoculant biological substance in liquid suspension in a media or solvent, and constituting a single dose, is loaded onto the multiple points of each inoculator so that the pre-selected amount of liquid suspension is retained on the exterior surfaces of the points and in the spaces between the points. This may be accomplished by pipetting as in FIG. 1 or by dipping as in FIG. 6. With such an arrangement, the resultant of the capillary forces, or surface tension, generated by the clustered points acting against the forces of gravity, provides a fairly precise control means for insuring that the clustered points are not over-loaded and that they will each retain thereon a substantially precise amount of biological substance in liquid suspension. After the inoculators each have been substantially precisely loaded with a uniform dosage of liquid substance, then they are subjected to a process of lyophilization so as to lyophilize the inoculant biological substance in situ on the inoculators.

The lyophilization process is generally well established, and in the specific processing involved herein it includes taking the supply of inoculators that are uniformly loaded with inoculant material in liquid suspension and placing them under aseptic conditions into a refrigerated lyophilization chamber that is then closed and maintained initially at 40 C. to 50 C. at atmospheric pressure in order to freeze the liquid on the inoculators. The inoculators are kept at this temperature for a time sufiicient to effect complete freezing of all liquid and to insure a uniform temperature in the inoculators and the frozen substance thereon. A period of 24 hours has been found to be adequate, although lesser time periods probably would be equally satisfactory. The freezing chamber is then evacuated of the air or gas therein, and the frozen substance on the inoculators then dries from the frozen state in vacuo, thereby giving up its liquid content and leaving the dried biological substance in situ tightly adhering to the exterior surfaces of the points and firmly retained in the spaces between the points. The chamber temperature is gradually raised to C. by the gentle means of an infrared heat source directed to the interior of the chamber. This heating serves additionally to drive off any residual moisture and completes the drying operation. The chamber is finally vented with sterile dry nitrogen or other inert gas, and finally the inoculators, each carrying there on a single-stable-dose of dried inoculant material, are packaged individually in the absence of air so that the pressure-points with lyophilized biological thereon are maintained, for purposes of achieving long shelf life, in an enclosed space from which air is caused to be absent and preferably in the presence of sterile dry nitrogen. This procedure will yield a lyophilized material in which the residual moisture content is no more than 1%, which is a desirable and attainable specification for purposes of producing a reliable instrument having extended shelf life.

While the foregoing description broadly describes the general method employed in effecting mass production of multiple-point pressure-puncture type intradermal inoculators which would serve as reliable single-stable-dose inoculators, certain additional steps are preferred in order to achieve desirable quality of production. First of all, the biological substance in liquid suspension is the form in which the inoculant is to be loaded onto the points of the inoculators. Desirably a relatively large supply of liquid is provided for continuous production technique and the liquid suspension is desirably chilled in a liquid reservoir at a temperature maintained at about -l0 C., so as to inhibit undesirable aging, reaction, or activity of the biological substance. Furthermore, desirably the liquid suspension is agitated, by stirring or the like, to maintain uniformity of concentration of the suspension. In the preferred form, as hereinafter described, the chilled liquid is located in an aspirated container that contains therein a magnetic mixer that is driven by a motor driven magnet positioned outside the container. The chilled and agitated liquid is then delivered for loading onto the points of the inoculator.

While the loading of inoculators may take place in a variety of manners as indicated, for example in FIGS. 1, 6 and 10, the concept of utilizing gravity forces as a control for effecting substantially precise and uniform loading of the inoculators prior to lyophilization is considered to be of substantial significance. It will be understood that the inoculators, since they are made of plastic that may be precisely molded, themselves provide a clustering of points that generate substantially uniform retentive forces of surface tension and/or capillarity. However, when a plurality of such inoculators are inverted and immersed in a bath and then Withdrawn, the act of separation of the inoculator points from the bath would normally tend to cause some variations in the excess of liquid retained on the points, but with the inoculators maintained inverted, the gravity forces soon correct any such variations and stabilize the dosages retained by the inoculators. In the practice of the procedure with the apparatus of FIG. 1, the same corrections are effected by the procedure of first loading the rack of inoculators on the right whose points face upwardly but at an incline to limit overloading, and then inverting the rack as shown on the left prior to the rack being moved to the lyophilization chamber.

In any event, it is also preferred that the racks be inverted, that is with the inoculator points pointing downwardly, when delivered into the lyophilization chamber and maintained there.

In the examples shown in the drawings, the apparatus is for loading multiple-point inoculators of the type disclosed in US. Patent No. 3,136,314 with smallpox vaccine. The inoculators 10 '(FIG. 2) are molded of a plastic material preferably methyl methacrylate resin, and defines both a scarifier portion and a split rin of frusto-conical cross-section adapted for thumb mounting as disclosed in Patent No. 3,062,212. The base portion 12 of the scarifier portion of the inoculator has fiat inner and outer sides 12a and 12b, with a platform 14 of regular shape, such as circular or square, located centrally on base 12 and projecting abruptly from said base portion 12. A group of nine (9) needles, or points 16 project from platform 14 and are closely clustered in a regular pattern of 3 X 3 needles. The volume of vaccine that can be held in the spaces between the needles when the needles are pointing downwardly is in the range of about 0.0l+ ml. of smallpox vaccine. The split ring portion of the inoculator includes arcuate thumb-embracing elements 18a and 18b.

The smallpox vaccine used is a glycerin-free, bacteriafree liquid smallpox vaccine containing a preservative such as 0.5% phenol; or a combination of 0.27 mcg. neomycin sulfate, 0.5 units polymycin B. Sulfate, and 0.03 mcg. tetracycline may be added to the liquid vaccine. Any one of several liquid smallpox vaccinal preparations suitable for lyophilization may be employed, such as that obtained from the chick chorio-allantois, as described by Jackson et al., J. Immunol. 77, 332-9 (1956), or that derived from a purified elementary body suspension derived from sheep pulp, described by Collier, J. Hyg. 53, 76-101 (1955). While the examples herein disclose use of smallpox vaccine it will be understood that the processes and apparatus may also be satisfactorily employed with other vaccines or inocula, such as tuberculin, which are effected by intradermal administration and which are susceptible of being lyophilized.

In FIG. 1, a rack 20 is provided in the form of a base 22 with a peripheral flange retainer 24 for positioning on the base a plurality of mounts 26 each of which has a shaped stud 28 for receiving thereon one of said inoculators 10. The rack 20 with a plurality of inoculators thereon is positioned upright but inclined, as seen in FIG. 1, with the inoculator points 16 facing upwardly.

A supply of chilled liquid smallpox vaccine V is provided in aspirator bottle 30, from whose upper end extends an aspirator tube 32 filled with a cotton filter, and from whose lower end extends tubular discharge stud 34 through which the liquid is withdrawn. A magnetic steel stirrer bar 36, encased in a plastic T, such as Teflon, to prevent reaction with the liquid, is within the bottle 30. The bottle 30 rests on a casing 38 which encloses therein a drive magnet 40 that is driven by a motor M controlled by controller C. The rotating magnet 40 causes bar 36 to rotate within bottle 30 and to agitate the liquid V. The liquid contents V of bottle 30 are cooled in any known way, such as by locating the entire bottle 30 and its stirring drive in a refrigerated chamber. The bottle 30 and its agitating drive are shown enlarged relative to other elements in FIG. 1 for purposes of clarity.

A motor driven pipetting machine, generally indicated at 42 is provided for drawing liquid from bottle 30 through tubular stud 34 into tubing 44, and thence through a controllable tubular hand dispenser 46 for discharge through a minutely orificed dispensing tip 48, the said pipetting machine being well known in the art. The pipetting machine, as is shown, is adjustable to measure out a single drop of desired size for each stroke.

After each inoculator 10 has been loaded to its capacity with liquid vaccine, as shown, for example in FIG. 2, the rack is moved from the position in the right-hand side of the stand in FIG. 1 to a position as shown to the lefthand side in FIG. 1 with the rack 20 and inoculators therein inverted. The previous left-hand tray may be moved to the lyophilization chamber that is described hereinabove. During the time period when the next tray 20 on the right is being loaded with the pipetting apparatus, the forces of gravity acting on the inverted inoculators on left-hand tray 20 are operative to effect the necessary draining of excess vaccine so as to obtain uniform liquid loading of the inoculators.

After loading and then draining of excess liquid, the other process steps are successive as shown in FIG. 5 where the process runs from left to right. The trays of inoculators are moved into a lyophilization chamber where the liquid is lyophilized, then dried in a vacuum, and then dried at a raised temperature. The last step of packaging is, as indicated earlier, carried out in the absence of air, and in the presence of inert gas, preferably such as dry nitrogen. The final product may be in the form of FIG. 3 where the inoculator 10 with lyophilized vaccine V thereon is completely packaged in a sealed air-tight plastic envelope containing dry nitrogen in the space S. Alternatively, as shown in FIG. 4 the inoculator 10 is provided with a circular base portion 12 having a peripheral groove 50 for receiving therein an O-ring type seal 52, and a cover 54 may be slip-fit onto circular base portion 12 so as to enclose the points 16 with lyophilized vaccine V thereon. The cover 54 has an inner peripheral groove 56 for receiving seal 52 thereinto so as to be air tight, and dry, sterile, nitrogen gas fills space S. Cover 54 is provided with outwardly extending flanges 58 for purposes of manipulating cover 54 onto and off the circular base portion 12'.

A preferred form of apparatus for effecting both loading of the liquid on the points of the inoculators and for eiTecting draining, under gravity, of excess of liquid is shown in FIGS. 68. Here a metal base 60, preferably aluminum or stainless steel, is shaped to define a plurality of parallel channels, or troughs 62, that are to be maintained and filled with liquid vaccine. The aluminum base 60 permits of cooling of the liquid in channels 62 if desired, or necessary. Otherwise, liquid is pumped or fed under pre-selected pressure from a supply such as aspirator bottle 30 with discharge stud 34 through a feed tube 64 which branches at 64a and 64b and connects to the bottom of each trough 62 for supplying liquid thereinto.

A peripherally framed tray 68 is provided which carries thereon a plurality of spaced, elongated, inoculator holders, or mount bars 70. Each mount bar 70 is shaped to define a stem, or neck, 72, and an enlarged head 74. The width of the neck 72 is such as to be slidably received between the spaced edges of the thumb-embracing elements 18a and 18b, as seen in FIG. 9. The shape or cross section, of the enlarged head 74 is generally oval and is so selected as to approximate the smallest enclosed inner area of the split ring thumb mounting, so as to permit a sliding of the split ring mounting onto and along the neck and head of the mount bar 70. A portion of head 74 provides a fiat surface 76 for abutting cooperation with the flat inner surface 12a of the inoculator. Removable end plate brackets 77 are provided which connect, by set screws, to the free ends of mount bars 70 and which engage the outer edges of the outer inoculators after each bar is entirely loaded with inoculators 10. While the latter arrangement which maintains the inoculators in tight edge-to-edge engagement operates to maintain the inoculators properly positioned at a set attitude on the mount bars 70 even when a tray 68 is inverted, it is proposed to provide alternative means that will insure that the inoculators will be maintained at the selected attitude. To this end, each mount bar 70 is provided with a track means in the form of an inclined tang, or rail, 78 projecting at an incline from the said flat surface 76, and the inoculators 10 are formed with a cooperating element in the form of an elongated groove inclined inwardly of surface 12a, thereby providing a slot for receiving the tang 78 therein as the inoculators 10 are slid endwise onto the mount bars 70, as best seen in FIG. 9. The latter arrangement insures that the inoculators 10 are maintained at a selected attitude relative to bars 70 for all attitudes of the tray 68. The four corners of tray 68 are apertured as at 79 to provide means for suspending the tray 68 from a hoist. Alternatively, the apertures 79 may serve as guideways for slidably receiving therein guide rods 79a that are fixedly secured to base 60.

Large numbers of inoculators may be loaded upon tray, or rack 68 and thereby efficiently handled for each step throughout the entire process. Specifically the mount bars 70 are of aluminum, which may be conveniently extruded to obtain the specific shape desired, and the bars are appropriately secured to the frame of tray 68 by any of several mechanical means, such as screws, welding or the like. The total size and capacity of tray 68 may be varied for coordination with other equipment used in the process. A typical rack providing ten mount bars 70, each 60 inches long and spaced 1 /2 inches apart on center lines, will hold 1500 inoculators of the type disclosed. The oval shape of head 74 is defined with a inch large diameter and inch small diameter, thereby closely approximating the smallest inside size and shape of the inoculator 10. The two sides runs 68a of tray 68 serve as support bars or legs for sliding engagement on shelf type supports that are normally provided in sterilization and lyophilization chambers.

The base 60 provides parallel channels 62 that are, for example, 7 inch deep by inch wide and spaced 1 /2 inches apart on centers. The number and length of channels correspond with the number and length of mount bars 70 on tray 68.

The construction of the base 60 and the tray 68 is such that when arranged in cooperative relation as best seen in FIG. 6, the inoculators 10 carried by mount bars 70 are positioned to be disposed vertically above the channels 62 in which the liquid inoculant is disposed. The width of the channels 62 are relatively small as compared to the channels length, but the width is of an order to permit entrance thereinto of the points 16 on one inoculator 10. In the process of loading the inoculators 10, the tray 68 is lowered to the position as seen in FIG. 6 with the points 16 projecting downwardly into the liquid in the channels 62. The top wall of the base 60 engages surface portions 12b of the inoculators 10 so as to permit only the points .16 to dip into the liquid vaccine. The rack 68 is maintained in the position of FIG. 6 for a few minutes permitting the surface tension and capillarity of the closely clustered points 16 to act upon the liquid to draw same up into the spaces between the points 16 and to thereby load the points with vaccine. The tray 68 is then moved vertically upwardly away from base 60, and such vertical movement is preferred, as it operates to prevent smearing of the vaccine and further the loading of liquid is thereby better controlled in response to the resultant force attained between the capillarity forces acting against the forces of gravity.

Within a very short time after the points 16 have been withdrawn from the vaccine bath, the excess vaccine will have drained off the points 16, thereby leaving on each inoculator a substantially identical loading of liquid, which in the case of smallpox vaccine is in a desired amount of about 0.01+ ml. The steps of loading and draining of excess vaccine takes about five minutes. The loaded inoculators 10 are then moved to a lyophilizing chamber where the remaining steps of the process are initiated as described hereinabove.

After inoculators are loaded onto rack tray 68 and locked in position, and before the loading process herein described is initiated, the loaded trays 68 are sterilized in a gas sterilizer for 4 hours with an appropriate and well known ethylene oxide gas mixture at 136 F., at 55% relative humidity and 18 psi. sterilization chamber pressure.

After the lyophilization procedure herein described, the loaded trays 68 are transferred to a packaging chamber filled with dry nitrogen gas. The inoculators with lyophilized material thereon are then sterile packaged under aseptic conditions in the presence of said dry nitrogen gas, in a well known manner, as by sealing each inoculator in its own envelope as in FIG. 3, or by capping each inoculator with a sterilized cap 54. In packing the inoculator in its own envelope, the inoculator is first removed from tray 68; while capping may be effected when the inoculators are still mounted on rack 68, and after capping, the capped inoculators are removed from tray 68.

An alternative inoculator loading operation is disclosed in FIG. 10 wherein liquid drops are dispensed downwardly from pipetting dispensers onto points 16 of inoculators. This process is conducted in a chamber maintained at C. Liquid is fed from a refrigerated reservoir (not shown) maintained at C. into a bank of automatic pipetting machines each similar to that shown in FIG. 1, and whose number corresponds with the number of mount bars 70 on rack tray 68. The tray 68 is disposed on a platform P with pipette dispensers 48' carried by frame means 90 and located directly above the points 16 on the first inoculator on each bar 70. The platform P with tray 68 thereon is moved by a linear indexing conveyor (of any well known type) which is timed or otherwise appropriately actuated, to automatically advance platform P a distance of /8 inch (spacing between centers of adjacent clusters of points 16) at the end of each cycle. The pipettes 48 are arranged to automatically dispense a precise amount of fluid in timed sequence after the platform P has advanced each step of inch. The regulation and control of the cycle may, for example, be controlled by means of a cam strip 92 carried on platform P with low dwell points located at inch spacing to correspond with the advancing of platform P, and with a roller type feeler 94 arranged to enter the low dwell points to initiate the cycle of dispensing from the pipettes followed by another advance of platform P.

While there has been disclosed herein the various steps of a process for efficient'ly producing single-stable-dose in. oculators and apparatus for carrying out such process, it is to be understood that this disclosure is merely by way of example and it is contemplated that equivalent steps and machines may be substituted.

What I claim as new, and desire to secure by Letters Patent of the United States is:

1. An apparatus for effecting loading of a biological substance in a liquid suspension onto the multiple-point portions of multiple-point type intradermal inoculators, said apparatus comprising, in combination: means defining a base having a plurality of elongated channels therein, in which biological substance in a liquid suspension is to be maintained, the width of each channel being relatively small as compared to the channels length but of a width size in the order to afford entrance thereinto of the points of a single multiple-point inocculator, a supply of biological substance in a liquid suspension carried in the channels in said base, an inoculator-carrying rack defining spaced, elongated, inoculator holders including means operatively associated with cooperating means on said base for registering said holders with the elongated channels in said base, so that the multiple points of all inoculators carried on said holders may be simultaneously immersed with the points pointing downwardly into the liquid in said channels and said rack means comprising a frame, a plurality of spaced bar means thereon, each of said bar means being coextensive with and corresponding to a separate one of said channels, each bar means in crosssection defining a support portion with an enlarged head, and said enlarged head including a rail element along the longitudinal extent thereof whereby said inoculators mounted on said elongated heads may be angularly retained.

2. An apparatus for effecting loading of a biological substance in a liquid suspension onto the multiple-point portions of multiple-point type intradermal inoculators, said apparatus comprising, in combination: means defining a base having a plurality of elongated spaced channels therein which biological substance in a liquid suspension is to be maintained, the width of each channel being relatively small as compared to the channels length but of a width size in the order to afford entrance thereinto of the points of a single multiple-point inoculator, a supply of biological substance in a liquid suspension, conduit means connected to each channel for feeding the biological substance in liquid suspension from said supply to each of said channels, means for agitating the supply of biological substance in liquid suspension delivered to said conduit means, an inoculator-carrying rack arranged to carry a plurality of inoculators with the points of the inoculators pointing downwardly and to simultaneously immerse and withdraw the downwardly facing points of said inoculators from the said liquid suspension in said channels, said base means including means to align said rack therewith and said rack means comprising a frame, a plurality of spaced bar means thereon, each of said bar means being coextensive with and corresponding to a separate one of said channels, each bar means in crosssection defining a support portion with an enlarged head, and said enlarged head including a rail element along the longitudinal extent thereof whereby said inoculators mounted on said elongated heads may be angularly retained.

3. An apparatus as in claim 1 wherein said inoculators are of the type that is provided with a split-ring type mounting that defines a frusto-conical ring recess for wedging application upon a thumb and said support portion comprises a neck whose width is smaller than the spacing of the adjacent segments of the split-ring type mounting.

4. An apparatus as in claim 3 wherein said enlarged head has a shape in cross-sectional area that approximates the smallest enclosed inner area of said split-ring type mounting, so as to permit of sliding of the splitring type mounting onto and along said neck and enlarged head.

5. An apparatus as in claim 2 wherein said rail element comprises an inclined tang extending from said bar 5 means.

References Cited UNITED 10 Gordon 118-500 X Neville et a1 118-425 X Hagemeyer 211-13 X Campell 118-425 X Zuercher 118-29 Dean 40-195 Latawiec et a1 134-88 X MORRIS KAPLAN, Primary Examiner US. Cl. X.R. 

